Heat sinks cool mechanical and electrical components by removing thermal energy. For example, modern electronics use a variety of electrical components (e.g., microchips) that generate significant amounts of thermal energy during operation. In order to protect these electrical components from excess heat, the electronics may thermally couple to a heat sink. Normally a heat sink continuously removes thermal energy from the electrical components and transfers it to the environment through convection, conduction, and/or radiation. However, some of these components may operate in unsteady cooling conditions. In other words, the heat sink's ability to transfer thermal energy to the environment through conduction, convection, and/or radiation may be temporarily or permanently limited. Unfortunately, existing systems may not effectively cool a mechanical or electrical component in these unsteady cooling conditions.